Drills suitable for producing blind- or through holes have been known for a long time in the woodworking industry, but those known drills are suitable for drilling holes only of low depths and the surface quality of the walls of the hole is also not satisfactory. The technical book "Faforgacsolo Szerszamok" (Muszaki Kiado publisher, Hungary, 1984) describes drills which are suitable for producing holes of such kind.
The disadvantage of the known wood augers is generally that the cut chips are guided by the cutting edges into a narrow space where the chips are accumulated and can cause clogging to such an extent that the cutting edge often burns off or peels off.
The formation and the pitch of the spiral shape of known shell bits is not suitable for assuring the transporting of the chips outward from the borehole. The known shell bits fill in the entire cross section of the hole, so the transporting of the chips is hindered. Therefore, these known augers are not suitable for continuous operation. The accumulation of chips in the borehole can be eliminated in the case of known auger bits only by lifting the drill out of the borehole several times during drilling, therefore the drilling efficiency is very low.